Jose Mourinho expressed his amazement at Iker Casillas’ salary at new club Porto and also insists teams are trying to get around Financial Fair Play rules.

The Chelsea manager appears to have reignited his feud with former Real Madrid goalkeeper, who he dropped from the team during his time at the club. The 34-year-old left to join Porto earlier this month and is set to pick up a reported salary of £1.7 million.

Mourinho also criticized at the amount Porto paid for French defender Giannelli Imbula. In an interview with the Guardian, he said, “This season Porto pays €20m for Imbula, it gives Casillas an amazing salary. Sporting [Lisbon] is paying millions for coaches and players. Football breaks every situation.”

The Portuguese also referred to Raheem Sterling’s £49 million move to Manchester City from Liverpool. He added, “This season we are saying: ‘Oh, look at this amount for Sterling’. But it will be worse next season. Next season someone will pay £60m.

“Football is like this — one season it is Financial Fair Play, the next is a way to dribble [past] the Financial Fair Play.

“It doesn’t upset me. I’m happy with the way that we are doing things. I am happy for the challenge of fighting against this power.”

The 52-year-old also insisted that his relatively unchanged squad must improve as the club’s rivals spend big. “It’s a big challenge. To be better with the same people, the players have to be better individually than they were last year,” he added. “So when they think: ‘Oh last season I did great,’ this season it is not enough.”